1. Field of the Invention
The present invention relates to a press machine of the class in which the first and second crankshafts are connected with each other by means of a connection mechanism including a pair of links.
2. Prior Art
Press machines using a link mechanism such as a knuckle joint, a toggle joint and so forth, are already known to the public. For instance, an example of such is disclosed by the Japanese Patent Appln. Public Disclosure (KOKAI) No. 9-225686. This press machine includes a first crankshaft rotated by a driving source and a second crankshaft connected with a slide. These crankshafts are connected with each other by means of a connection mechanism using three of links.
In the prior art press machines of this kind, however, the stroke of a slide motion in the up and down directions is limited to a preset value determined depending on the sorts of press processings such as the precise press processing (low speed press processing), the stamping processing (high speed press processing) and so forth.
Consequently, in the prior art press machine of this kind, the stroke of the slide can not be changed, so that the applicable range of the press machine has been limited by such limited stroke of the slide.
Therefore, in the press machine of this kind, it is important that the stroke of its slide motion in the up and down directions be made variable.